FCTT-222-021

FCTT
INPUT 8 CIRCUITSCOMMUNICATION SPECIFICATION
Modbus RTU

FCTT-222-021

Content

1. Communication specification ･･････････････････････････････････････････････

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2. Transmission and reception protocol ･･････････････････････････････････････

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3. Calculation method of CRC-16 ･････････････････････････････････････････････

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4. Communication process flow chart ･････････････････････････････････････････

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5. FCTT communication terminal arrangement ･･････････････････････････････････

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6. Modbus protocol RTU mode ･････････････････････････････････････････････････

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6.1 Function code ･････････････････････････････････････････････････････････

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6.2 Abnormal response ･････････････････････････････････････････････････････

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6.3 Measurement value data request ････････････････････････････････････････6

6.4 Model information request ･････････････････････････････････････････････

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7. Communication monitor function ･･･････････････････････････････････････････

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FCTT-222-021

1. Communication specification(1) Specification
ItemSpecification

Standard

TIA-485-A (2003)

Transmission system

Half-duplex two-wire system

Synchronous system

Asynchronous communication method

Modulation code

NRZ

Transmission character

BinaryCable length

1000m (The total extension)

Error detection

CRC-16 (X16＋X15＋X2＋1)

Number of connections

Max. 32 unitsConnection method

M3 screw connection (FW11 socket / Mounting base, FWBA)

Transmission data are sent out from a bit 0.
(2) Communication setting
Item

Setting range

Factory setting

Bit rate

4800bps / 9600bps / 19200bps / 38400bps

Start bit

1 bit (Fixed)

Data length

8 bit (Fixed)

ParityNONE / Odd number / Even number

Stop bit

1 bit：Parity / 2 bits：Non parity

Communication address

01 to 999600bps－－Even number
1 bit (Parity)
00 (Communication unused)

2. Transmission and reception protocol(1) Usual request (Query)To a response, it takes the following time.
4800bps：18 to 20ms
9600bps：13 to 15ms
19200bps：11 to 13ms
38400bps：10 to 12ms
Address

Master side
Address

Function
code

Data

CRC

Address

Function
code

Data

Slave(FCTT) side

CRC

Function
code

Please spare the following time
till the next transmission.
4800bps：Over 10ms
9600bps：Over 5ms
19200bps：Over 5ms
38400bps：Over 5ms(2) The timeout between data
Please make the interval between data must be 1.5 characters or less.
If there is an interval of 1.5 character hours or more, a timeout error will occur.
Please make the interval between data must be 1.5 characters or less.
4800bps：Below 3.5ms
9600bps：Below 1.9ms
19200bps：Below 0.9ms
38400bps：Below 0.5ms
Address

Functioncode

Data

CRC

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FCTT-222-021

3. Calculation method of CRC-16

CRC-16 is adopted as error checking in Modbus RTU mode.
An address, a function code, and data are calculated by the following method.
(1) Arithmetic process

CRC-16① 2 bytes of data-area X is secured to a CRC calculation.
Data X←FFFFH
Assignment② FFFFH is substituted for ① as initial value.
③ XOR of data X and the nth data (n=1) is calculated.
Assign it to data X.
④ The 1-bit right shift of the data X is done.

Data X ←Data X XOR nth data

⑤ If carry occurs in operation of ④, data X and XORof A001H are taken.
⑥ Operation of ④,⑤ is repeated until it shifts 8 times.

Data X
1 bit right shift

Carryoccurrence ?
No⑦ The next data (n+1) and XOR of data X is calculated.
Assign it to data X.
YesData X ←Data X XOR A001H⑧ Operation of ④ to ⑦ is repeated until processingof all data is completed.
⑨ 1 byte of upper and 1 byte of lower of data-area X
for a CRC calculation are exchanged.

(2) Example of calculation
No

8 times shift
End ？
Yesn+1No

CRC Object range
1 byte1 byte2 bytes

2 bytes

Address Function code Data address Request data

2 bytes
CRC

All data end？

01H
Yes
The upper and lower
byte of data X,exchange

END

304H

00H00H00H

19H

31C0H

FCTT-222-021

4. Communication process flow chart
Idle

Data receiving

Local address ？

NoYES
ErrorError check

NormalFunction codecheckError

NormalData-address
range check

Out ofrange

NormalDatatransmission

Error codeanswer

5. FCTT communication terminal arrangement

Terminal arrangement

FCTT＋－SG

SHIELD100Ω
Inside commonR

Ter.

－

①②③
④⑤⑥№

Terminal symbol①②③④⑤⑥＋－SGSHIELD
Ter.
－Terminal №FW11FWBA
1132
44632758・By short-circuiting the Ter. terminal and thenegative terminal (⑤ and ⑥), a terminating
resistance of 100Ω is connected.
・SHIELD terminal (④) is a relay terminal for the shieldedwire of the communication cable.
There is no connection with the internal circuit.
・The terminal arrangement is different between the FW11
socket and the mounting base FWBA.
(Refer to the above terminal number)

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FCTT-222-021

6. Modbus protocol RTU mode
6.1 Function code

The next function code is supported with this product.
Function
code

Name

Data address

Specifiable
number of data

Master → FCTT

FCTT → MasterCommand message[Unit：byte]

Response message[Unit：byte]

Min.

Max.

Min.

Max.

04H

Measurement range data

30001 to 30125

Max. 125 words

88725503H

Model information

40501 to 40503

Max. 3 words887116.2 Abnormal response

In case the message transmitted from the master is judged to be abnormal, this product does the next abnormalanswer.
(1) In case it becomes a no answer①：In case a message transmission error occurs. (Overrun，Framing，Parity error，CRC)②：In case the data interval of a message exceeds a regulation value (1.5 characters).
③：In case the message frame exceeding 8 bytes is received.
(2) In case as answered in an error code.
In the error that does not correspond to (1), the following abnormal response is returned.
At this case, the code that applied 80H to the code of a demand is returned to a function code.
And, the generated error code is returned as data.
1 byte1 byte1 byte2 bytes

Addressfunction code(+80H)

Error code

CRC

01H

84H

02H

C2C1H

Error code list
Operation code

FunctionContents

01H

Undefined function code

Received a function code that the slave does not have.
(Non-existent function code)

02H

Abnormal data address

A data address that is not defined for the slave was specified.
(Outside the address range)

03H

Number of abnormal data

More data was requested than the number of data to be returned.
Or, the number of reply data requested was 0 words.

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FCTT-222-021

6.3 Measurement value data request

Read the measurement value from this product. There is no broadcast. Function code is 04H.
(1) Data request (Query)
In case it performs setting value request, it is necessary to designate the start address of data to acquire.
When sending a data address, specify a relative address (30001 is subtracted from the address in the dataaddress table).
Please assign the word number of requested data as the number of data.
12345Function Read start addresscode(Relative address)

Address

01H

678

Number of data

CRC

0000H

0008H

F1CCH

Relative address

Data address

Memory contents

Data type

0000H

30001

INPUT1 Measurement value data

WORD

0001H

30002

INPUT2 Measurement value data

WORD

0002H

30003

INPUT3 Measurement value data

WORD

0003H

30004

INPUT4 Measurement value data

WORD

0004H

30005

INPUT5 Measurement value data

WORD

0005H

30006

INPUT6 Measurement value data

WORD

0006H

30007

INPUT7 Measurement value data

WORD0007H

30008

INPUT8 Measurement value data

WORD

04H

Data address list
Function code04(2) Response
If measurement value requirements are performed normally, the following response will be returned fromthis product side.
Example) Read start address：30001, Number of data：8, Measurement value data (INPUT 1 to 8)：10000
12

345Address

Function
codeAnswer
bytecount

INPUT1
Measurement value
data

INPUT2
Measurement value
data

INPUT3
Measurement value
data

INPUT4
Measurement value
data01H

04H

10H

2710H

2710H

2710H

2710H

1213141561671781891910201121

INPUT5
Measurement value
data

INPUT6
Measurement value
data

INPUT7
Measurement value
data

INPUT8Measurement value
data

CRC

2710H2710H

2710H2710H

DEDFH(3) Measurement value data format
Input
DC4 to 20mA
DC1 to 5V

Transmission data(hexadecimal)

Transmission data(decimal)

Measurable range

0H to 2710H

0 to 10000-25％ to 125％ of span
(Transmission data -2500 to 12500)

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FCTT-222-021

6.4 Model information request

Used to read type code from this product.
There is no broadcast. Function code is 03H.
(1) Data request (Query)
In case it performs model information request, it is necessary to designate the start address of data toacquire.
When sending a data address, specify a relative address (40001 is subtracted from the address in the data
address table).
Please assign the number of requested data as the number of data.
1234

5678Address

Function
code

Read start address(Relative address)

Number of data

CRC

01H

03H

01F4H

0001H

C404H

Data address list
Function code

Relative address

Data address

01F4H

40501

Model information Type code

01F5H40502

Not used (0000H)

01F6H

40503

Not used (0000H)

03H

Memory contents(2) Response
If model information request are performed normally, the following response will be returned from thisproduct side.
12

3

4

5

6Address

FunctioncodeAnswerbyte
countType code

CRC

01H

03H

02H

0021H

785CH

 Model information. Type code

TypeCommunication data

FCTT (Input 8 circuit)

0021H

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FCTT-222-021

7. Communication monitor function

This function is valid only when using communication.
The communication status is determined by the lighting status of the RUN LED.
The communication monitor specifications are as follows.
CommunicationstateCommunication monitor

Definition

RUN LED status

Priority

When there is communication addressed to thelocal station and the reply is normal.
(Even if it recovers from the abnormal state,
it is judged to be normal)
・No communication has been achieved after
applying the auxiliary power supply.
・Set to a communication address that is not
used for communication

Always on

Abnormality

・Time out
・Communication error (Parity error /Overrun error / Framing error), CRC error

Blinking at 1 second cycle1(0.5 second on, 0.5 second(Top priority)
off)

OthersSetting error
・Change communication setting while applying
power (Operates with the communication
settings before the change)

Blinking at 2 second cycle(1 second on, 1 second off)

NormalNot
communicating

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FCTT-222-021

Tokyo Office : 11-13, Hitotsuya 1-chome, Adachi-ku, Tokyo, 121-8639, JAPAN.
TEL：+81-3-3885-2411 , Fax：+81-3-3858-3966
Kyoto Office : 1-19, Ichinobe-Nishikawahara, Jyoyou-shi, Kyoto, 610-0114, JAPAN.
TEL：+81-774-55-1391 , Fax：+81-774-54-1353
DATE：March 23, 2022

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